Furnace for heating glass plates for tempering



L. J.-B. FORBES 2,170,749

PLATES FOR TEMPERING Aug. 22, 1939.

FURNACE FOR HEATING CLASS Filed Feb. '7, 1936 3 Sheets-Sheet 1 III IIIarr-amp Aug. 22, 1939. 1.. J.-B. FORBES FURNACE FOR HEATING GLASS PLATESFOR TEMPERING s Sheets-Sheet 2 Filed Feb. 7, 1936 4 In. 4 H 2 m 5 I I 3,U" H 6 4 M 2 w "n H. 11 M w 2 L x r grvucm to r/ M y a4 3 Sheets-Sheet 3SUM .01 5

Aug. 22, 1939. J.-B. FORBES- FURNACE FOR HEATING GLASS PLATES FORTEMPERING Filed Feb. 7, 195a Patented Aug. I 22, 1939 a: oFricE FURNACEFOR HEATING GLASS PLATES FOR TEIlflERING Lewis Jex-Blake Forbes, St.Helens, England, assignor to The American Securlt Company,

Wilmington, Del.

Application February '1, 1936, erial No. 62,855 In Great BritainFebruary 21, 1935 Claims.

This invention relates to the tempering of glass and has for its objectanimproved furnace for heating the glass.-

In the heating of glass to be temepred, it has 6 been found advantageousto heat the glass in a plurality of furnaces, so that the glass may beheated rapidly at first and slowly at the end.

The multi-stage furnaces hitherto proposed for heating glass fortempering, when the glass, in

the form of sheets or plates, is suspended during the operations ofheating and cooling, have been so disposed that the glass, suspendedfrom a horizontal rail, enters the furnace at one end, through an enddoorway temporarily opened to admit the glass, passes through thesuccessive furnace stages, and leaves the furnace through an end doorwayat the other end.

It has been found that glass tempered after heating in furnaces of thistype, is liable to be defective in showing irregularities in tempering,

and these irregularities have been traced to variations in thetemperatures of the two end furnaces, caused by the opening of the enddoors. When a' door is opened, a strong current of air rises 26 throughthe furnace nearthe opening and cools the furnace at this end, and thefurnace therefore cannot be maintained throughout at a uniformtemperature.

According to the invention, the furnaces are 80 permanently closed tothe outer air except through slots in their top stones. In the shorttime during which a furnace is open to the air through the slot in itstop stone, no air current is formed in the furnace, and the upper partof 85 the-furnace near the slot is not appreciably cooled. The glassplates descend into the first furnace and rise out of the last furnacethrough the'slots in their top stones and there is a slot givingcommunication between these slots through 40 which the suspension meansof the glass plates are adapted to pass as the plates travel from thefirst to the last furnace. Each plate is preferably suspended from aplate 'adaptedto cover the slot in the top stone of each of the furnacesin suc- 45 cessiqn, A lower runway and an upper return runway may beprovided for the coverplate, each cover plate closing the slot in theiJDQaStOIlG of a furnace while on the lower runway; and means are thenprovided for lowering a cover plate from an the upper to the lowerrunway above the first furnace and of raising it from the lower to theupper runway above the last furnace.

In the accompanying drawings: Figure 1 is a side view of the apparatus,partly 55 broken away, with details omitted;

Figurez is a side view to a larger scale of the left hand end of Figure1 with portions broken away, and

h Figure 3 is a cross section through the centre line of the furnace ofFigure 2.

Referring to the drawings, l is the first furnace. 2 is the last, and 3,3, are intermediate furnaces of which there maybe any number; glassplates in the furnaces are shown in dotted lines at 4. The furnaces areall in a line, with a narrow passageway 5 from the first to the last,extending as a slot it through the top stone 6, and giving passage tothe glass plates 4, with their support ing tongs l, and the tong bars 8from which the tongs hang. The front wall of the furnace 2 has beenbroken away in Figure 2 to show these parts.

The first and last furnaces have end walls 9, so that the only openinginto the furnaces is the narrow slot l0 through the top stone 6. Theslot I0 is made still more narrow by the pieces ll, except in thecentral portions of the first and last furnaces, where free passage inand out of the furnaces is required for the tong bars 8.

Each tong bar 8 is suspended from a cover plate l2, extending the fulllength of each furnace, and faced with suitable heat insulatingmaterial. At each end of each cover plate I2 is a pedestal 13 carryingrollers M which run on angle irons I5, whereby the cover plates aresupported just clear of the-top stone 6. The angle irons l5 are attachedto angle irons l6 running the whole length of'the furnaces. These aresupported on. cross girders H which rest on uprights it.

Each cover plate I2 is provided with a bar with mushroom head l9. Abovethe first and last furnaces is suspended a girder 20 carrying tongs 2iadapted to engage the mushroom head bar Ill. The girder 20 is providedwith end blocks 22 which are guided vertically by the uprights 23,supported on the angle irons Hi. The two girders 20 are suspended byropes 24 from hoisting gear (not shown) above the upper frame members 25(Figure 1). By the ropes 24, the girders 20 can be lowered into theposition shown in Figures 2 and 3, and above furnace 2 in Figure 1, orraised ,into the position shown in dotted lines in Figures 2 and 3 andin full lines above furnace i in Figure 1. In the lower position of thegirder 20, the cover plate i2 rests with its rollers M on the angleirons l5, and in the upper position the cover plate it is raised so thatthe glass plate depend ing from it occupies the position of the plateitv above furnace l in File 1.. When in this latter position, the coverplate I! rests with its rollers l4 on-the channels 21, which (except forgaps to be explained later) extend the whole length of the furnaces, andare supported by hangers 28 from the upper frame members 25. The coverplate supporting the glass plate 29 (Figure 1) is seen in this position,in end elevation, in Figure 3, but the tongs 1 are not shown in thisfigure. I

In order that the rollers l4 may be able to reach the level of thechannels 21, gaps 30 are left in the channels above the last furnace 2,to give passage to the rollers. These gaps can be closed by twomembers3| pivoted at 32 to the uprights 23 and the channels 21 respectively.Rods 33 are pivoted to the members 3| at 34. In the position shown inFigures 2 and 3, the gaps 30 are open, and the cover plate l2 can beraised from the lower to the higher position, when so raised,

the rods 33 are drawn to the left, and thereby the members 3| close thegaps 39 by providing support for the rollers l4, and the cover plate canthen be run on the channels 21 from the position above the furnace 2into the position shown in Figure 1 in. which it is supporting the plate29. -A similar device is provided to close similar gaps above furnace I,so that a cover plate above this furnace can be lowered into the lowerposition.

When a cover plate I 2, with depending glass plate 4 is raised fromfurnace 2 into its upper position, the glass plate is then between apair of blowing frames 35, by means of which it can'be cooled. Thesupports for, and air pipes to, the blowing frames 35 are not shown. Thefurnace 2 "is shown with electrical heating. elements 36 arranged alongeach of its inner walls.

The operation of the apparatus is as follows, starting with thecondition that there is a plate of glass in each furnace: When the platein furnace 2 has remained there for the required time, the girder 20above the furnace is lowered so that its tongs 2| engage the mushroomheader bar l9. The girder 20 is then raised, drawing the plate but ofthe furnace, till the cover plate l2 has its roller I 4 on a level withthe channels 21, and then the rod 33 is drawn to the left to move themembers 3| to support the rollers l4. The plate isthen'between theblowing frames 35 and these are operated to cool it. As soon as theplate has been raised out of the furnace 2, the cover plate l2 overfurnace is moved to the left, pushing the cover plates to the-left ofit, until the extreme one is over furnace 2; each plate has then beenmoved into the next adjacent furnace to the left. As soon as thisoperation has been completed, the girder 20, supporting a cover platewith depending plate 26 over furnace is lowered, introducing the plateinto furnace I. The tongs 2| are then disengaged from the bar l9 and thegirder 20 returned to its upper'position. As soon as the first mentionedplate has been cooled, the cover plate from which it hangs is run alongthe channels 21 until the plate occupies a position such as that of theplate'29. The plate is then removed and a new plate is hung on the tongs1, and the cover plate is then run into position above furnace I, whereits bar i9 is engaged with the tongs 2| of the girder 20. This completesthe cycle of operations.

An auxiliary cover plate l2, with a tong bar, is preferably located tothe left of furnace 2 and so arranged as to close the slot in the topstone of the furnace automatically, as soon as the cover platepreviously on the furnace has been raised. To effect this, lugs 40depending from the plate are attached to cables 31 passing over pulleys38;

weights 39 on the cables then tend to move the cover plate to the rightto a position over furnace 2.

The operations of the above-described cycle may be effectedindependently, or the cyclical movement of the cover plates may beeffected automatically at timed intervals.

As an alternative to the above described cyclical operation, the glassplates, suspended from their tong bars may be run from the first to thelast furnace on a runway in the furnaces, through the intermediatefurnaces, if any. In this case, the girders 20 are permanently attachedto cover plates and the tong bars are detachably hung from the coverplates as by tongs such as the tongs 2|.

By means of this apparatus, the temperatures of the furnaces may be soadjusted that the rateof rise of temperature of the glass platesdiminishes as the plates approach the desired final temperature, and, byreason of the complete enclosure of the furnaces except for the narrowslot in their top stones, it is possible to maintain a uniformtemperature throughout each furnace. Since the temperature differencebetween any one furnace and an adjacent furnace is small, interchange ofheatbetween the furnaces by air currents in the passage way 5 is sosmall as not appreciably to affect the uniformity of temperature in anyone furnace.

Apart from its advantage in maintaining uniformity of temperature in thefurnaces, the in- .vention has the advantage of a lower heat loss glassplates for tempering, comprising in combinationa plurality of furnaces,top stones for the first and last furnaces provided with slots throughwhich plates can be inserted and removed respectively in a verticaldirection, suspension means for the plates, means adapted to permitmovement of the plates from the fifst furnace to the last furnace, anintermediate top stone provided with a slot giving communication betweenthe slots in the first and last top stones along which slot saidsuspension means are adapted to pass as theplates travel from the firstto the last furnace, and means adapted to permanently close the furnacesto the outer air except at the slots in the first and last top .stones.

2. A multi-stage furnace for heating vertical glass plates fortempering, comprising in combination a plurality of furnaces, top stonesfor the first and last furnaces provided with slots through which platescan be inserted and removed respectively in a vertical direction,suscover the slot above each of the furnaces in succession.

3. A multi-stage furnace for heating vertical glass plates fortempering, comprising in combination a plurality of furnaces, top stonesfor the first and last furnaces provided with slots pension means foreach plate, means adapted to through which plates can be inserted andremoved respectively in a vertical direction, an intermediate top stoneprovided with a slot giving communication between theslots in the firstand last top stones, suspension means for each plate, a cover plate bywhich said suspension means are supported, and a runway along which eachcover plate is movable to cover the slot above each of the furnaces insuccession and to carry a plate from the first to the last furnace.

4. A multi-stage furnace for heating vertical glass plates fortempering, comprising in combination a plurality of furnaces, top stonesfor the first and last furnaces provided with slots through which platescan be inserted and removed respectively in a vertical direction, anintermediate top stone provided with a slot giving communication betweenthe slots in the first and last top stones, suspension means for eachplate,

a cover plate by which said suspension means.

for lowering a cover plate from the upper to the lower runway above thefirst furnace and means for raising a. cover plate from the lower to theupper runway above the last furnace.

5. A multi-stage furnace for heating vertical glass plates fortempering, comprising in combination a plurality of furnaces, top stonesfor the first and last furnaces provided with slots through which platescan be inserted and removed respectively in a vertical direction, anintermediate top stone provided with a slot giving communication betweenthe slots in the first and last top stones, suspension means for eachplate, a cover plate by which said suspension means are supported, alower runway along which eachcover plate is movable to cover the slotabove each of the furnaces in succession and to carry a plate from thefirst to the last furnace, an up per return runway for the cover plates,means for lowering a cover plate from the upper to the lower runwayabove the first furnace means for raising a cover plate from the lowerto the upper runway above the last furnace and means adaptedautomatically to cover the slot above the last furnace when a coverplate is raised from the lower to the upper runway.

LEWIS JEX-BLAKE FORBES,

